The 70-year-old patient in the Auckland Hospital in New Zealand had suspiciously low blood pressure. The doctors were stumped. But they had an unusual experimental tool at their disposal: a unique computer program that analyzes a magnetic-resonance imaging (MRI) scan, measuring the motion of a patient’s heart and comparing it to that of a “healthy” virtual heart constructed not of blood and tissue but from mathematical equations. The analysis handed the clinic’s experts the smoking gun: part of the heart was twisting in a pattern often associated with a partially blocked valve, which, untreated, would probably kill the patient within three years.

To diagnose this disorder, surgeons would normally have to crack open the patient’s chest. But the software had accurately identified the problem in about 15 minutes. “It helps point out where the heart wall may be failing,” says Peter Hunter, the University of Auckland bioengineer whose team developed the software in collaboration with the German company Siemens.

The MRI analysis program is just one of a rapidly growing number of medical applications emerging from an ambitious global effort known as the cardiome project. The goal of this multilab endeavor is to build a virtual heart: a computer model that accurately depicts everything from a single cardiac cell up to the whole organ, from the interwoven electrochemical activities of millions of cells to the delicately synchronized pumping of blood. The model should even be able to “suffer” from the blocked arteries, weakened muscles, and erratic electrical rhythms that characterize heart diseases.

Medical researchers have been working on computer models of the heart for decades. But thanks to exponential leaps in available computer power, rapid progress in describing the precise and complex details of how the heart actually works, and the fashioning of mathematical representations of those details, increasingly lifelike models of the heart are beginning to yield real health dividends. Insights gleaned from the virtual-heart project are leading to new approaches to diagnosis, surgery, and drug discovery, with the potential to improve or even save the lives of the more than 13 million people in the United States alone who suffer ailments ranging from heart attacks caused by clogged coronary arteries to potentially fatal abnormal heartbeats triggered by rare genetic mutations. “We can do a good job now of modeling on a computer what happens to cardiac cells in heart failure, and predicting how a heart contraction will respond to a drug or other stimulus,” says Andrew McCulloch of the University of California, San Diego, a leading researcher in the field. “It’s allowing us to answer a lot of experimental and clinical questions.”

The virtual heart is a work in progress that does not yet mimic many of the intricate and still mysterious genetic, cellular, and mechanical processes that take place in real hearts. Nevertheless, as the project’s computer models improve over the next several years, they could revolutionize the diagnosis and treatment of heart disease by casting new light on the complex workings of the organ, and serving as tools for quickly and cheaply testing drugs, diagnostic devices, and surgical treatments that are still too risky to try on humans.